The cell walls of all plant have a basic framework provided by high-strength nanofibers having about 4 nm wide called cellulose microfibrils. When plant fibers such as pulp are fibrillated to the level of cellulose microfibrils, microfibrillated cellulose is obtained that forms nanofibers having an extended-chain crystalline structure. Some types of known microfibrillated cellulose originate in bacteria (mainly acetic acid bacteria). Nata de coco is one well-known example of food using such microfibrillated cellulose. Because microfibrillated cellulose is known to possess desirable properties such as strength and lightness of weight, attempts have been made to improve the strength and other properties of resin by blending it with microfibrillated cellulose (for example, see Patent Document 1).
In one method, resin, such as phenolic resin, is added to microfibrillated cellulose. However, this lowers the fracture strain, and makes the product fragile. In some cases, it even lowers the strength of the resin. Accordingly, there is a need to find ways to improve properties such as strength and fracture strain.
Meanwhile, cellulose is classified into types I, II, III, and IV, according to its crystalline structure. Type-I cellulose includes naturally occurring celluloses (for example, cotton), and microfibrillated cellulose. Type-I cellulose is known to change its crystalline structure and becomes type-II cellulose when immersed in a sodium hydroxide aqueous solution.
Patent Document 1: JP-T-9-509694